Recently, global warming comes into problem with the increase of carbon dioxide emissions, and the suppression of CO2 discharged becomes an important issue in the iron industry. As to such an issue, the operation with a low reduction agent ratio (abbreviated as low RAR, total amount of a reducing material blown through tuyeres and coke charged from a top of the furnace per 1 ton of pig iron) is driven forward in the recent blast furnace operations. Since coke and pulverized coal are mainly used as a reducing material in the blast furnace, in order to attain the low reduction agent ratio and hence the suppression of carbon dioxide emissions, it is effective to replace coke or the like with a reducing material having a high hydrogen content ratio such as waste plastic, LNG, heavy oil or the like.
Patent Document 1 discloses a technique wherein a solid reducing material, a gaseous reducing material and a combustible gas are simultaneously blown with a plurality of lances to promote the heating of the solid reducing material in a combustion field of the gaseous reducing material. In this technique, it is said that the combustion rate of the solid reducing material can be improved to suppress the generation of unburned powder or coke breeze to thereby improve the air permeability and decrease the reduction agent ratio. Patent Document 2 discloses a technique wherein a lance is multiple-tube type and, for example, a solid reducing material is blown through an inner tube and a combustible gas is blown from a gap between inner tube and middle tube and a gaseous reducing material is blown from a gap between middle tube and outer tube. Further, Patent Document 3 discloses that a plurality of small-size tubes are arranged around a main tube of the lance in parallel.